(a) **Prime cost method**

\[
\$30{,}000 \times \left(\frac{1}{5}\right) = \$6{,}000
\]

**First-year deduction: $6,000**

(b) **Diminishing value method**

\[
\$30{,}000 \times \left(\frac{2}{5}\right) = \$12{,}000
\]

**First-year deduction: $12,000**

**Controlling authority:** Division 40 of the *Income Tax Assessment Act 1997* (Cth), the capital allowances rules for decline in value of depreciating assets.